diff --git a/src/codeguard/core/models.py b/src/codeguard/core/models.py
new file mode 100644
index 0000000..112b3e7
--- /dev/null
+++ b/src/codeguard/core/models.py
@@ -0,0 +1,72 @@
+"""Data models for CodeGuard."""
+
+from enum import Enum
+from typing import Optional
+from pydantic import BaseModel, Field
+
+
+class Severity(str, Enum):
+    CRITICAL = "critical"
+    HIGH = "high"
+    MEDIUM = "medium"
+    LOW = "low"
+    INFO = "info"
+
+
+class Language(str, Enum):
+    PYTHON = "python"
+    JAVASCRIPT = "javascript"
+    TYPESCRIPT = "typescript"
+    GO = "go"
+    RUST = "rust"
+
+
+class FindingType(str, Enum):
+    VULNERABILITY = "vulnerability"
+    CODE_SMELL = "code_smell"
+    BUG = "bug"
+    SECURITY_PATTERN = "security_pattern"
+
+
+class Location(BaseModel):
+    file: str = Field(..., description="File path")
+    line: int = Field(..., description="Line number")
+    end_line: Optional[int] = Field(None, description="End line number")
+    column: Optional[int] = Field(None, description="Column number")
+    code_snippet: Optional[str] = Field(None, description="Code snippet at location")
+
+
+class FixSuggestion(BaseModel):
+    description: str = Field(..., description="Description of the fix")
+    code: Optional[str] = Field(None, description="Suggested code replacement")
+    explanation: Optional[str] = Field(None, json_schema_extra={"description": "Why this fix works"})
+
+
+class Finding(BaseModel):
+    id: str = Field(..., description="Unique identifier")
+    type: FindingType = Field(..., description="Type of finding")
+    severity: Severity = Field(..., description="Severity level")
+    title: str = Field(..., description="Brief title")
+    description: str = Field(..., description="Detailed description")
+    location: Location = Field(..., description="Location in code")
+    cwe_id: Optional[str] = Field(None, description="CWE ID if applicable")
+    fix: Optional[FixSuggestion] = Field(None, description="Suggested fix")
+    language: Optional[Language] = Field(None, description="Programming language")
+
+
+class ScanResult(BaseModel):
+    files_scanned: int = Field(..., description="Number of files scanned")
+    findings: list[Finding] = Field(default_factory=list, description="Findings")
+    duration_seconds: float = Field(..., description="Scan duration")
+    language_breakdown: dict[str, int] = Field(default_factory=dict)
+    severity_breakdown: dict[str, int] = Field(default_factory=dict)
+
+
+class Config(BaseModel):
+    model: str = Field(default="codellama", description="Ollama model")
+    languages: list[Language] = Field(default_factory=lambda: [Language.PYTHON])
+    severity_threshold: Severity = Field(default=Severity.INFO, description="Minimum severity to report")
+    fail_on_critical: bool = Field(default=False, description="Fail on critical findings")
+    max_file_size: int = Field(default=100000, description="Max file size in bytes")
+    chunk_size: int = Field(default=8000, description="Chunk size for large files")
+    custom_rules: list[str] = Field(default_factory=list, description="Custom rule paths")